The present invention relates to a water dispensing apparatus, which provides filtered water free of specific microorganisms, and comprises means for assuring the filter integrity. The dispensing apparatus of this invention is particularly intended for drinking water in domestic use.
Various types of domestic drinking water purification systems, which claim to provide microorganism-free filtered water, are known in the art The most commonly used systems remove protozoan cysts, such as cryptorsproridium Parvum and giaria Lablia, which may be found in insufficiently chlorinated water supplies. As the cysts are from 5-10 microns in size, they are typically removed by a one micron rated microporous filter element, usually fabricated from carbon block, so that it simultaneously removes chlorine and other impurities to improve taste. Submicron microporous filters fabricated from ceramic or synthetic polymeric materials, with a maximum pore size of 0.2 micron, are also known. Such filters are capable of removing pathogenic bacteria such as pseudomonas Aurigena, which may also be found in domestic, treated water supplies. The danger is that the users of such filters may be given a false sense of security at times when such organisms are discovered in the local water supply and a xe2x80x9cboil waterxe2x80x9d alert is issued by the authorities. Although several such filters may be performance-tested when certified for the validity of their claims, few, if any, claim to 100% quality assure every filter unit sold Thus, some finite fraction of units sold do not in fact meet the claimed retention In addition, the filter element might either have been damaged prior to being installed, or might be improperly installed by the user in the housing, such that leakage of unfiltered water into the final product is possible. Finally, glue seals to the filter in the fabricated filter element can sometimes fail over time in an aqueous environment, depending on factors such as pH and temperature and the number of mechanical shocks given to the system during opening and closing the water supply to the system. In all of the above instances, since such purification systems do not comprise means for testing the integrity of the filter, the user has no way to verify if the system will in fact perform according to claimed performance specifications.
Means for testing filter integrity are also known in the art. Thus, U.S. Pat. No. 4,872,974 discloses a membrane filter testing method, which comprises increasing the pressure at the primary side of a membrane filter fixedly accommodating the housing and wetted with a liquid, by a gas at a predetermined rate, and checking whether the pressure at the primary side of the membrane filter is within a specified judging range after the lapse of a predetermined period of time.
U.S. Pat. No. 5,417,101 discloses a method and apparatus for isolating defective filter elements by measuring a gas flow rate under known pressure conditions through said elements.
U.S. Pat. No. 5,594,161 discloses a method of testing the integrity of a filter element in a filter assembly which includes wetting the filter, subjecting the inlet side of the filter to a gas pressure, measuring the pressure in the outlet conduit as a function of time, and determining whether a pressure measurement at a preselected time exceeds a reference pressure by a predetermined amount.
An article entitled xe2x80x9cPredicting . . . Removal Performance of membrane Systems using In Situ Integrity Testingxe2x80x9d, published in Filtration and Separation, January, February 1998, pp. 26-29, describes two main methods for testing membrane systems integrity, the first of which consists in applying air at a pressure bubble point to one side of the membrane, isolating and then measuring the declining pressure over time. The bubble point hereinbefore referred to, or more exactly, the bubble point pressure, is defined as the pressure required for forcing the air to flow through the pores of a membrane whose pores have been initially completely filled by a liquid. The other method consists in filling the shell of the module with a liquid and allowing the air leakage to displace liquid from the shell. The flow rate of displaced liquid is then a direct measure of the membrane integrity.
The testing methods of the prior art, as summarized hereinbefore, and in general, all the methods of the art, require the measurement of a physical quantity, be it a volume or a pressure, and therefore, a certain degree of expertise on the operator""s part and the presence of the required measurement components. They are, therefore, unsuited to a domestic drinking water apparatus. On the other hand, domestic apparatus should be provided with methods for testing the integrity of the filter, to avoid the danger of a supply of unsafe water.
It is therefore a purpose of this invention to provide a domestic water-dispensing apparatus that is provided with the means for testing the integrity of the filter.
It is another purpose of the invention to provide a domestic water-dispensing method and apparatus that do not require the measurement of physical quantities, and judge the integrity of the filter by visual inspection or by sensing of a physical property for the presence of air bubbles.
It is a further purpose of this invention to provide such a method and apparatus that are simple and of simple and secure operation and require no expertise on the user""s part.
It is a still further purpose of this invention to provide a domestic water-dispensing apparatus, comprising means for determining the filter integrity, which are simple in structure and operation and economical.
It is a still further purpose of this invention to provide a domestic water-dispensing apparatus, comprising automatically controlled means for determining the filter integrity.
Other purposes and advantages of the invention will appear as the description proceeds.
The water dispenser with filter tester according to this invention comprises:
1xe2x80x94a water container,
2xe2x80x94a filter contained within a pressurizable housing having an inlet and a dispensing outlet connected to the filtered fluid side of the filter;
3xe2x80x94a source of pressure;
4xe2x80x94first valve and conduit means for leading water from said container to the filter housing inlet; and further comprises:
5xe2x80x94means for feeding gas to said filter housing inlet to generate gas pressure at said inlet;
6xe2x80x94a pressure gauge or transducer for monitoring the pressure at the filter housing inlet; and
7xe2x80x94control means for controlling said gas feeding means to cause or stop said feeding.
In a form of the invention, the means for feeding gas to said filter housing inlet comprise:
axe2x80x94a reservoir,
bxe2x80x94second valve and conduit means for controlling the level of the water in said reservoir; and
cxe2x80x94third conduit and valve means for connecting said reservoir to said filter housing at a second inlet;
and the control means for controlling the gas feeding to the filter housing inlet comprise third valve and conduit means to permit or prevent the admission of water into said reservoir.
In said first form of the invention, the source of pressure is preferably a pump or a cylinder containing compressed gas and provided with valve and conduit means for controlling the admission of compressed gas from said cylinder into said water container. If the source of pressure is a pump, said second valve and conduit means connect said reservoir to said pump and/or to said filter housing inlet or disconnect said reservoir from said pump and/or said filter housing inlet If the source of pressure is a compressed gas cylinder, said second valve and conduit means connect said reservoir to said water container when compressed gas has been admitted into it and/or to said filter housing inlet or disconnect said reservoir from said container and/or to said filter housing inlet.
In a second form of the invention, the source of pressure is a compressed gas cylinder provided with valve and conduit means for controlling the admission of compressed gas from said cylinder into said water container, and the means for feeding gas to said filter housing inlet comprise conduit and valve means for feeding gas to said filter directly from said gas cylinder.
In said first form of the invention, said second valve and conduit means, when open, selectively allow said source of pressure to feed water into said reservoir, whereby to displace air therefrom or to draw water therefrom, selectively to cause water partially to fill said reservoir to a predetermined, normal level or to a higher testing level.
Said third conduit and valve means, when open, permit to introduce into said second filter housing inlet air displaced by water fed into said reservoir and to displace air and/or water from the inlet side of said filter housing. Preferably, said filter housing is provided, in addition to said dispensing outlet, with a second outlet on the inlet side of the filter, which is more preferably a feedback outlet connected to conduit means for returning, to said water container, water displaced from said filter.
The control means are programmed, in the first form of the invention, so as to actuate the source of pressure when said second valve and conduit means connect it to said reservoir, and stop it when said pressure measurement means indicates that the air pressure at the filter housing inlet has reached a predetermined test pressure, which is lower than the bubble point pressure of the filter. The predetermined air pressure is chosen in relation to the pore size and function of the filter and the meaning of the test of integrity. If one defines gross mechanical failure as a defect of 10 microns or more, then the predetermined integrity test pressure is set at a value whose minimum is 0.2 bar , and whose maximum is a pressure equal to 80% of the bubble point pressure of the filter.
In said second form of the invention, the conduit and valve means for feeding gas to the filter directly from said gas cylinder are activated to stop said gas feeding when the pressure at the filter housing inlet has reached said predetermined test pressure, lower than the bubble point pressure.
If at the test pressure bubbles appear at the filter housing outlet, this means that filter integrity is lost. Then an alarm, with which the dispenser is provided, gives an acoustic or optical alarm signal, such as e.g. a warning light or a writing, to indicate that the integrity of the filter has been compromised and water from the outlet may not be of the specified purity which the filter is meant to deliver. The machine is then disactivated until the filter has been replaced. If no bubbles appear at the filter outlet, then the filter is normally fictional and the water is restored in the reservoir to a normal level, and the apparatus can be used, immediately or whenever required, as a filtered water dispenser.
It will be understood, therefore, that the water dispenser of the invention has three modes: the inactive mode, the dispensing mode, in which it operates as a conventional dispenser, and the testing mode, in which it permits a test of the integrity of the filter. In the inactive mode, all valves are closed. In the dispensing mode, the first valve and conduit means are open. In the test mode, gas is fed to the second filter housing inlet The control means are programmed to place the water dispenser in the dispensing or the testing mode, or to inactivate it, depending on a command which the dispenser user can give in any convenient, even conventional, way, e.g. by means of a key or keys connecting it to or disconnecting it from a power source, whether a power line or an independent source, such as battery, or selectively controlling circuits of a microprocessor, or the like. The dispenser is inactivated when it is efficient, but no water is to be dispensed, or when the filter is being replaced. After the test has been terminated and the filter has been replaced or it has been found that it should not be replaced, the apparatus is inactivated and is ready to be returned to the dispensing mode, or is directly returned to it It also follows logically from the above that the control means to the apparatus may be programmed to automatically carry out some combination of the three modes upon a single command by the user. Thus, after each dispense activation, or some preset number of dispense activations, the test may be automatically initiated.
While the invention is of particular interest for domestic water dispensers, this is not a limitation of the invention, since it is applicable to water dispensers in general, including industrial or public dispensers, regardless of their size or their specific use.
Correspondingly, the invention comprises a method for testing a filter contained within a pressurizable housing in a household water dispensing apparatus, which, in the first form of the invention, comprises the following steps:
1xe2x80x94providing a reservoir,
2xe2x80x94feeding water into it to a predetermined level; when it is desired to test the filter:
3xe2x80x94filling the filter housing with water and forcing water into all pores of the filter,
4xe2x80x94feeding water into said reservoir to raise the water level therein, while allowing air contained therein to flow out of said reservoir into the second filter housing inlet; thereby displacing the water contained in the inlet side of the filter housing through the second outlet,
5xe2x80x94monitoring the air pressure at the second filter housing inlet;
6xe2x80x94discontinuing the feeding of water into said reservoir when said pressure has become the test pressure; and
7xe2x80x94verifying whether air bubbles appear in the water issuing from a filter housing outlet, and if they do appear, substituting the filter, while if they do not appear, using the dispensing apparatus in the normal way.
It is obvious that the water is fed into the reservoir by means which depend on the source of pressure, and thus by pumping it if the source of pressure is a pump or by connecting the reservoir to the water container when this latter is under gas pressure, if the source of pressure is a compressed gas cylinder.
In the second form of the invention, after the housing and filter have been filled with water, the method comprises testing the filter by:
Ixe2x80x94feeding gas to the housing inlet from the compressed gas cylinder;
IIxe2x80x94monitoring the air pressure at the filter housing inlet;
IIIxe2x80x94discontinuing the feeding of gas when said pressure has become the test pressure; and
IVxe2x80x94verifying whether air bubbles appear in the water issuing from a filter outlet, and if they do appear, substituting the filter, while if they do not appear, using the dispensing apparatus in the normal way.
Since raising the water to the higher level serves to create the predetermined test pressure by compressing the air above the water, different level ratios of the test level to that of the normal level may be adopted in individual cases, depending on the dimensions of the various parts of the apparatus, to achieve the correct pressure.
The filter be of any used in a water dispensing apparatus, particularly domestic ones, but may be, for example only, a microporous, 0.2 micron filter prepared from a synthetic polymer, such as polysulphone or nylon, or an inorganic polymer such as a ceramic material. Such filters have a bubble point pressure, when wetted with water, from 3.5 to 4.5 bar. Typically, such filters have intrinsic pure water flows of 20-40 cc/sq.cc. filter area/bar.
The volumes of the various parts of the apparatus depend on its use. By way of example, in a domestic dispenser, the water container may have a capacity from 0.5 to 5 liters, and the reservoir a volume from 50 cc to 1.5 liter.
The invention further comprises a method of operating a water dispenser, particularly a domestic one, having an inactive, a dispensing and a test mode, which comprises placing the dispenser in the test mode, carrying out the testing method hereinbefore described, substituting the filter if it is found to be faulty, and placing the dispenser back into the dispensing mode.